How to specify timing constraints between 2 memory ports

Use get_fanouts. There should be a number of posts in this forum, but something like:

set fouts [get_fanouts {enable_register_name}]

set_multicycle_path -setup 2 -from $fouts -to $fouts

set_multicycle_path -hold 1 -from $fouts -to $fouts

If it's a divide-by-2 register(i.e. it feeds back on itself), you might need to remove it from the group using remove_from_collection. Also, many designs don't use the -from, just the -to, since all paths to these registers are multicycles.